Chris, yep 7 hours has a bit of fat in it, but he has to make a $, and if you trust him then it should be jake.
Just had my gearbox done, and labour was from a dedicated gearbox place a little less than that, but they were chasing the box rebuild as business, so hours to remove and install, plus fit up a new clutch kit and skim flywheel.
Now in saying that, the ring gear must be real shot for him to need to replace it, but age of vehicle my be contributing factor
To do this he will need to pull flywheel, remove old ring gear, heat the new and shrink fit to your current flywheel, so box and clutch kit out first to do.
Just for peace of mind, when he gets it ready to do and pulls the starter motor, fit the replacement "first" and test, before anything else is removed.. Its not hard to test and three bolts, plus cable remove and install. Be a pain in the you know what to find out all you really needed to do was just the starter.